Atoms
What is an Atom?
An atom is the tiny particle that makes up all matter — everything you can see, touch, or even breathe!
Parts of an Atom
1. Nucleus (center)
Contains:
Protons (positive)
Neutrons (no charge)
It is very small but very heavy (most of the atom’s mass is here)
2. Electrons (outer part)
Very tiny particles with negative charge
Move around the nucleus in paths called shells or orbits
Charges in an Atom
Protons = positive
Electrons = negative
Neutrons = no charge
Normally, atoms are neutral (equal protons and electrons)
Types of Atoms (Elements)
Different atoms make different elements.
Examples:
Hydrogen (H) → simplest atom
Oxygen (O) → helps us breathe
Carbon (C) → found in all living things
All elements are arranged in the Periodic Table
Atomic Number
The number of protons in an atom
Example:
Hydrogen = 1 proton → atomic number 1
Oxygen = 8 protons → atomic number 8
Atomic Mass
Total of protons + neutrons
Ions (charged atoms)
Sometimes atoms lose or gain electrons:
Lose electrons → become positive ion
Gain electrons → become negative ion
Molecules
Atoms join together to form molecules:
Water = H₂O
Carbon dioxide = CO₂
Amazing Facts
Atoms are so small that millions can fit on a pinhead!
Easy way to remember:
Atom = nucleus (protons + neutrons) + electrons around